Lesson1.1

Three building blocks of geometry are points, lines, and planes. A point is the most basic building block of geometry. It has no size. It has only location. You represent a point with a dot, and you name it with a capital letter. The points shown below can all be called P... P

A Line Is a straight, continuous arrangement of infinitely many points. It has infinite length, but no thickness. It extends forever in two directions. You name a line by giving the letter names of any two points on the line and by placing the line symbol above the letters, for example, AB or BA.

A Plane A plane has length and width, but no thickness. It is like a flat surface that extends infinitely along its length and width. You represent a plane with a four-sided figure, like a tilted piece of paper, drawn in perspective. Of course, this actually illustrates only part of a plane. You name a plane with a script capital letter, such as P.

Collinear and Coplanar Collinear means on the same line. Coplanar means on the same plane.

In Plane p, points A and B and coplanare

A Line In geometry, a line has no thickness but its length extends in one dimension and goes on forever in both directions. Unless otherwise stated a line is drawn as a straight line with two arrowheads indicating that the line extends without end in both directions. A line is named by a single lowercase letter,, or by any two points on the line,.

Line segments vs. Rays A line segment consists of two points called the endpoints of the segment and all the points between them that are collinear with the two points. A ray begins at a point and extends infinitely in one direction. You need two letters to name a ray. The first letter is the endpoint of the ray, and the second letter is any other point that the ray passes through.

Congruency ≅ vs. equality = Two segments are congruent if and only if they have equal measures, or lengths.

Midpoint The midpoint of a segment is the point on the segment that is the same distance from both endpoints. The midpoint bisects the segment, or divides the segment into two congruent segments.

1)Name all segments with midpoints.2)Use this diagram to express congruency and equality.